The present invention relates to data networks, and more particularly, to devices, methods and computer program products for generating a status report that affirms and/or denies receiving data blocks.
Modern wireless networks are fast incorporating packet data features similar to those found on local area networks, such as those based on Ethernet. For example, the General Packet Radio System (GPRS) was developed as a packet data network for the Global System for Mobile Communications (GSM), the predominant cellular phone standard in the world. The GSM cellular phone uses Gaussian Minimum Shift Keying (GMSK) as the modulation on the Physical Layer. The GSM specification has gone through several revisions, each adding enhancements to the network. One revision of the specification added higher data rates through the use of adaptation between 8-ary Phase Shift Keying (8PSK) and GMSK on the Physical Layer. The changes in the Physical Layer are the essence of the Enhanced Data Rates for Global Evolution (EDGE) component of the modern GSM/EDGE Network. As part of the GSM EDGE Radio Access Network, GPRS was enhanced to include the changes to the Physical Layer, in addition to changes in the Radio Link Control (RLC) and Media Access Control (MAC) sublayers to allow for performance improvements via the use of adaptive coding and incremental redundancy, a form of Type II Hybrid Automatic Repeat Request (ARQ) procedure. Enhanced GPRS is abbreviated in the specification as EGPRS.
In EGPRS, the RLC/MAC layers on either side of the network are situated at the Mobile Station (MS) and the Base Station Subsystem (BSS). The peer RLC/MAC entities communicate using Radio Blocks of one or more RLC/MAC Protocol Data Units (PDU). Each PDU is numbered using a Block Sequence Number (BSN). In acknowledged mode, the BSNs are tracked by the sending and receiving RLC/MAC entities to allow for erroneous blocks to be corrected by the sending of additional and incremental information to aid decoding. For downlink (BSS to MS) status, the BSS polls the MS to request the status of received blocks, and the MS replies with a status report within a required period of time. For uplink (MS to BSS) status, the BSS periodically sends a status report to each communicating MS.
In GPRS, the window sizes for the ARQ are small, allowing for the status report to be sent in one unnumbered block as a bitmap. In EGPRS, the window sizes vary according to the coding scheme and may be much larger than that used in GPRS. Very often, the status report may not fit into one packet as a bitmap alone. Therefore, the specification requires the use of compression of the bitmap using run-length coding. The compression method is a minor modification of the compression tables specified for ITU T.4 compression. Requests for status of received blocks and thereto in GPRS packet networks are described in the 3rd Generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; General Packet Radio Service (GPRS); Mobile Station (MS)—Base Station System (BSS) interface; Radio Link Control/Medium Access Control (RLC/MAC) protocol 3GPP TS 04.60 V8.16.0, September 2002 (“the 3GPP TS 06.60 specification”).